The invention relates to multilayer diagnostic assay elements and, more particularly, to the use of materials therein which are suitable for immobilizing biological species such as proteins in a specific layer of the element.
Various types of diagnostic assay elements for the rapid analysis of analytes or metabolites in a biological fluid have been described. Generally, a sample of a biological fluid, e.g., plasma, serum, etc., is applied to the assay element and as a result of the interaction between an analyte or metabolite of interest and the reagent(s) present in the assay element a detectable change corresponding to the analyte or metabolite is brought about. The detectable change can be a color change which may be evaluated visually or read spectrophotometrically such as with a densitometer. In another scheme based on the presence of fluorescent - labeled biological species a fluorescent output signal is generated and read spectrofluorometrically.
Thin film multilayer assay elements which are suitable for carrying out immunometric assays have been described in the art. These thin film multilayer elements typically include a support carrying at least one reagent layer and a light blocking layer to permit the signal - generating species in one layer to be read out without interference from materials present in another layer. The elements may also include other layers to perform various functions such as, for example, a registration layer for holding a signal - generating species formed in or released from another layer.
In various of the assay methods it is required that a biological species, e.g., an antigen or an antibody be immobilized in a reagent layer and that such species remain in the particular layer throughout the assay. It is known to covalently bind proteinaceous materials such as antigens or antibodies to a matrix material such as agarose to form a reagent layer in such assay elements. However, this immobilization technique is not satisfactory in all instances. It is also known in immunometric assays carried out with classical wet chemistry methods to utilize proteins which are immobilized by being bound to polymeric bead materials. In these assays the biological species which do not interact with the immobilized proteins are typically removed from the reaction zone by means of a wash step. However, a wash step is typically not utilized with thin film multilayer assay elements because there is no provision for removal of the wash liquid which would include the unreacted reagents.
Therefore, there is a continuing need for new materials which can be used to provide various functions in multilayer assay elements.
It is therefore an object of the invention to provide a novel biological diagnostic assay system.
Another object of the invention is to provide multilayer biological diagnostic assay elements which include glyoxyl agarose, an aldehyde group derivatized agarose, in one or more layers.
A further object is to provide multilayer diagnostic assay elements for analytes having a molecular weight of about 5000 or less.